Battery powered power tools are widely used in many fields because of portability. Rechargeable lithium battery packs with advantages in weight and capacity are one of the best battery choices for power tools. Lithium battery packs have special charging requirements for safety and efficiency, however.
A common charging system for a lithium battery pack includes a charger that outputs power having a constant current or constant voltage for charging a battery pack which has a nominal voltage. A disadvantage is that a charger is only operable to charge a corresponding battery pack. In addition, a common charger provides different charging parameters based on information of the battery cells which are stored in the battery pack. A disadvantage is that the charger needs to obtain the relative information of the battery pack before charging, and then confirm the charging parameter, which is obviously complex.